1. Field of the Invention
The present invention relates to a fuel control apparatus for an internal combustion engine, in which the quantity of air taken into the internal combustion engine is detected by utilizing a Karman vortex stream phenomenon and the quantity of fuel supplied to the internal combustion engine is controlled on the basis of this detection output.
2. Background Art
When a cylindrical body is set in a flow of fluid, the flow is separated from the surface of the cylindrical body in the vicinity of the opposite sides of the body so as to alternately generate vortexes on the opposite sides. The vortexes grow to form a vortex stream which flows downstream. This vortex stream is called a Karman vortex stream and such a phenomenon as described above is widely known. As disclosed in, for example, Japanese Patent Publication No. 13428/76, there have been proposed a variety of apparatuses in which the number of generated Karman vortexes is counted so as to detect the velocity of flow of the flow rate of the fluid generating the Karman vortices based upon the fact that the number of generated Karman vortexes is closely dependent on the velocity flow of the fluid.
In the case where such a Karman swirling flow rate detection apparatus as described above is provided upstream of a throttle valve of an internal combustion engine, that is, in an air intake path, it measures the quantity of air sucked into the internal combustion engine. However, there is a problem that the Karman swirling flow rate detection apparatus may measure the quantity of air taken into and occupying the air intake path between the throttle valve and the engine in addition to the quantity of suction air taken into the combustion chambers when the throttle valve is rapidly opened. As a result, the thus measured value exceeds the quantity of air actually sucked into the internal combustion engine. Therefore, if the quantity of fuel supplied supply to the internal combustion engine is controlled on the basis of the thus measured value, the fuel-air ratio disadvantageously becomes overrich. In order to eliminate this disadvantage, there has been proposed such a technique that the quantity of suction air is limited so as not to exceed a predetermined value. In this proposal, however, there has been such a problem that it is impossible to properly control the quantity of supplied fuel.